MINING magnate Gina Rinehart asked troubled swimming legend Grant Hackett to intervene in her family’s bitter court dispute, urging him to ask her daughter Bianca — Hackett’s ex-girlfriend — to withdraw her trustee nomination “rather than be found a liar in the witness box”.

Bianca, the eldest daughter of Australia’s richest person, yesterday became the first in the family to actually step inside a courtroom for the legal battle that has spanned more than two and a half years, as part of her bid to become trustee.

She defended her brother John’s remarks about their youngest sister, Ginia — the only one of the four children to side with their mother in the dispute — being an ­“oxygen thief”.

The Supreme Court heard Olympic champion Hackett was contacted by Mrs ­Rinehart on June 22 in a bid to stop her daughter taking the stand in support of her trustee nomination.

Bianca Rinehart, who married Rio Tinto executive Sasha Serebryakov in Hawaii last year with no member of her family present, dated the swimming star in the early 2000s with the pair attending Ian Thorpe’s 21st birthday.

“Suggest you advise her urgently please, no money is worth this, she should withdraw her nomination as trustee rather than be found a liar in the witness box,” the email said. Court documents show Hackett then forwarded the email to Bianca.

“Just got this from your mum. It probably means very little but do you want to discuss it with Sash/lawyers ... Good luck. You’ve done the hard yards and you’re ­obviously in a great position. Cheers, Grant.”

Bianca Rinehart said she did not always “approve of the language” used by her brother, but insisted the pair were acting in the family’s best financial interest.

“He does not want to see the family business left to somebody who is not up to the job,” she told the court.

The almost $5 billion trust, which controls more than 23 per cent of the shares in the family flagship company Hancock Prospecting, was established by Lang Hancock in 1988. Mrs Rinehart relinquished the role as trustee last year, after two years of courtroom disputes.

The court heard Bianca Rinehart would not rule out further legal action against her mother if appointed trustee by Justice Paul Brereton.

“If there is an area of concern which I feel may not have been properly handled by (Mrs Rinehart), I would ask the advisory (independent) trustee if it required further examination ... and I would take it to court for judicial advice,” she said.

Richard McHugh, SC, acting for Ginia, asked Ms Rinehart about comments she made about John Hancock being a “destructive” family member and “an idiot”. “You were deeply concerned about John’s ‘bite the hand that feeds’ approach ... John’s drive for money ... ,” he said.